In a clear warning to Syrian President Bashar al-Assad, U.S.Secretary of State John Kerry said President Barack Obama wasconsulting with allies and members of Congress and would decidesoon how to respond to the Aug. 21 attack.

"President Obama believes there must be accountability forthose who would use the world's most heinous weapons against theworld's most vulnerable people," Kerry said, making clear thatWashington blames Assad for what he called the large-scale,indiscriminate use of chemical weapons against civilians.

"The indiscriminate slaughter of civilians, the killing ofwomen and children and innocent bystanders by chemical weaponsis a moral obscenity."

Military chiefs from the United States and its European andMiddle Eastern allies met in Jordan for what could be a councilof war, should they decide to punish Syria.

Many hundreds of people died in Damascus suburbs in whatappears to have been the worst chemical weapons attack sinceIraqi leader Saddam Hussein fatally gassed thousands of Kurds in1988.

U.N. investigators crossed the frontline from the centre ofthe capital, which remains under Assad's control, to inspect theMouadamiya suburb, one of at least four neighbourhoods hit bythe poison gas last Wednesday before dawn.

The United Nations said one vehicle in its convoy wascrippled by gunshots fired by "unidentified snipers." The teamcontinued on after turning back for a replacement car.

"I am with the team now," a doctor who uses the name AbuKaram told Reuters by telephone from Mouadamiya. "We are in theRawda mosque and they are meeting with the wounded. Our medicsand the inspectors are talking to the patients and takingsamples from the victims now."

Wassim al-Ahmad, an opposition activist, said members of theFree Syrian Army umbrella rebel organisation and theopposition's Mouadamiya Local Council were accompanying theinspectors on their tour of the suburb.

"The inspectors are now examining victims being treated at amakeshift hospital in Mouadamiya and are taking blood samplesfrom them," Ahmad said.

INTERVIEWING SURVIVORS

Video filmed at the site showed inspectors in black and bluebody armour and blue U.N. helmets walking through a street ascurious onlookers came up to watch.

They shook hands with men who appeared to be rebels wearingcamouflage vests, and were accompanied by doctors and residents.The group descended into the basement of a building where theywere told injured survivors were being treated to protect themfrom more shelling. Another video showed an inspectorinterviewing a patient and taking notes.

Activists say at least 80 people were killed in Mouadamiyawhen the district was hit with poison gas. Hundreds of peoplealso were killed in three other rebel-held districts - Irbin,Ain Tarma and Jobar.

An opposition activist said a large crowd of people gatheredto air their grievances to the U.N. inspectors, who planned totake samples from corpses.

The inspectors later returned to their hotel, and within anhour residents reported that the shelling of Mouadamiya resumed.

The decision to proceed with the mission despite comingunder attack thwarted an apparent attempt to halt their workbefore it began.

"The first vehicle of the Chemical Weapons InvestigationTeam was deliberately shot at multiple times by unidentifiedsnipers in the buffer zone area," the United Nations said in astatement. "It has to be stressed again that all sides need toextend their cooperation so that the team can safely carry outtheir important work."

Syrian state television blamed rebel "terrorists" for the shooting. The opposition blamed it on pro-Assad militiamen.

The inspectors had been stuck in a downtown luxury hotelsince the attack, waiting five days for government permission tovisit the scene a few miles away. They had arrived three daysbefore the incident, with a mandate to investigate earlierreports of more limited chemical weapons use.

ASSAD TOO LATE

Kerry said Assad's decision to finally allow access was toolate to be credible. "That is not the behaviour of a governmentthat has nothing to hide," Kerry said.

Kerry said the U.N. inspectors could at most confirm thatchemical weapons were used, not who used them, but that it wasAssad's government that has such weapons and the means ofdelivering them. He said Washington had additional informationon the attack that it would share soon.